Kidney or bladder problem

["guest@endurance.net" <guest@endurance.net>]

Terry Emmitt tle01@health.state.ny.us
Hi... I'm looking for some antedotal information on problems 
with blood in the urine - not tying up (at least I think not).  
My 21 yr old Qh gelding has just been put back into work over a
two month period, starting with an hour of light riding and 
working up to trot/canter work for 20 minutes of it.  Last week,
His urine after work was dark brown.  I called the vet and he
said, work him, then I'll come out and take blood.  At the 
beginning of that ride, the urine was yellow, by the end it
was dark red.  The blood test showed 'nothing alarming' and 
next I took a urine sample in (a yellow one, I didn't have the
heart to work him into red).  Well, today my vet advised me that
there is blood in the yellow sample.  He will be coming to do 
an exam later in the week.  He's not too informative, although
a very well respected horse vet.  Originally, he suspected tying up
but there was no indication in the blood.  He mentioned kidney 
or bladder and said I could keep him on turnout but not to ride
him.  

I searched the archives and found a comment from 'Linda' about
kidney stones.  Do anyone have comments on what it could be?  
Also, what if he does have stones or some sort of tumor? Are 
these problems indicative of the beginning of the end, or is it
something treatable or manageable?

Thanks for all your help....
Terry & Buddy